Heartbroken family members last night said their final goodbyes to a three-month-old baby boy after he was tragically killed in Friday's Melbourne CBD rampage.

Meanwhile, the devastated father of a 10-year-old girl horrifically killed in the Bourke St tragedy remains at the bedside of his other daughter, 9, and his wife, who were hurt in the carnage.

Grave concerns are held for the mother's health as she fights for life.

The young girl's death has plunged her family and friends into despair.

Advertisement

A classmate yesterday paid tribute to her friend. "She was always happy and knew how to make people smile," the student said.

Rabbi Yisroel said the family regularly came to his McKinnon synagogue, but yesterday it was unusual for them to be missing from the Sabbath service.

"She was a sweet girl," he said. "She was good hearted and always happy to help with community projects. It's a big loss; she's an innocent little girl."

Video will play in
Play now
Don't auto play

Never auto play

The family weren't able to use technology for most of yesterday due to their religious beliefs.

Police Chief Commissioner Graham Ashton revealed there were grave concerns for at least two injured victims in hospital.

"It may be that those numbers of people killed may still increase beyond four," he said yesterday before the death count rose from four to five deaths.

A family friend who runs a gym the sisters had attended spoke of his heartache. "Today we found out the identity of this family and realised with a sick feeling in my gut that these little girls were students who we know personally," he said.

"The public space where they were so terrorised is a space which belongs to every single one of us. We all feel helpless and hopeless at times like this as there is so little we can do."

A woman whose child was in the same class as the young girl struggled to comprehend the tragedy. "It hurt before I knew who it was but when I heard who it was, it hit even harder," the woman said. "It hurts as a mother because there are no words that can describe what they themselves are going through and what we go through is the hurt that somebody's hurting."

Friends of the 10-year-old deceased girl have started a fundraising page for the family.